Prussian blue derived iron oxide nanoparticles wrapped in graphene oxide sheets for electrochemical supercapacitors

Abstract

Hybrid materials have shown promising potential for energy storage applications, such as supercapacitors due to the combined properties or advantages of two (or more) individual constituents. In this work, we report the fabrication of a new composite which combines graphene oxide (GO) sheets with Prussian blue (PB) nanoparticles, which act as a precursor for iron oxide (IO). The GO/PB composite precursors with different GO : PB ratios can be successfully converted into nanoporous GO/IO hybrid composites through a thermal treatment in air at 400 °C. In the resulting GO/IO composites, the GO sheets are efficiently spaced due to the insertion of IO layers. Interestingly, the GO/IO hybrid (GO : PB ratio = 25 : 75) exhibits a higher surface area of 120 m² g⁻¹ compared to pure GO (34.9 m² g⁻¹) and IO (93.1 m² g⁻¹) samples. When employed as a supercapacitor electrode, the GO/IO hybrid (prepared from GO : PB = 75 : 25) showed a higher specific capacitance of 91 F g⁻¹ at a scan rate of 20 mV s⁻¹, compared to pure GO (81 F g⁻¹) and pure IO (47 F g⁻¹). The enhanced electrochemical performance of the GO/IO hybrid electrode may be attributed to the insertion of IO nanoparticles in between the GO layers which creates a well-spaced electrical transportation path for electrolytes and ions, whilst also enabling easy access for the electrolytes to the whole electrode surface. Furthermore, the presence of GO in the GO/IO hybrid composite helps to lower the resistivity of IO and increase the specific capacitance value of the hybrid, as a result of the improved conductivity.